Tag Archives: REPL

In this installment of “Functional programming without feeling stupid” I would like to show you how to define things in Clojure. Values and function applications are all well and good, but if we can’t give them symbolic names, we need to keep repeating them over and over.

Before we start naming things, let’s have a look at how Clojure integrates with Java. I’m assuming you are still in the REPL, or have started it again with lein repl.

Track 1: “If anyone should ask / We are mated”

As it happens, Clojure’s core library is lean and focused on manipulating the data structures of the language, so many things are deferred to the underlying Java machinery as a rule. For example, mathematical computation is typically done using the static methods in the java.lang.Math class:

user=> (java.lang.Math/sqrt 5.0)
2.23606797749979

As you can see, this is a function application like we have already seen in Part 1, but this time the function we are using is the sqrt static method in the java.lang.Math class.

Java 7 acquired Unicode character names, and they are accessed through
the getName method in the java.lang.Character class. This is no mean feat, since there are over 110,000 characters in the Unicode standard, and each of them has a name (although some of them are algorithmically generated). To find out the canonical character name of a Unicode character, such as the euro currency symbol, you would use the getName static method:

Hey, what’s wrong? Well, if you look up the documentation of java.lang.Character.getName, you will find out that it takes an int value as an argument, not a character. You can actually do this check from inside the REPL: